Adelaide: Recuperating Australian captain Michael Clarke will pass the most challenging fitness test to confirm his place in the World Cup squad, his long time personal trainer said Wednesday.

Cricket Australia has given Clarke, down with back and hamstring complaints, time till Feb 21 to prove his fitness. Australia play Bangladesh in their second pool match Feb 21.

There is growing concern in Australia that the co-hosts have to conduct their World Cup campaign without their regular captain.

But trainer Duncan Kerr said the 33-year-old was "giving it everything he possibly can to get it right and meet that deadline". He first worked with Clarke 17 years ago.

Kerr claims he is unaware of the specifics of the test Clarke must pass by Feb 21, saying "it's all pretty much hush-hush at the moment".

"Let's see what they throw at him and see how he goes," he was quoted as saying by the Sydney Morning Herald Wednesday.

"Michael's done everything that's asked of him from a training point of view, from the program that's been set by Cricket Australia to the program that the physio gives him, to what I've given him. He's passed everything so far.

"He wants to play cricket. It's what he does best and what he enjoys. He's had doubters all his career and he's always come out on top. He's played 108 tests. In his last test he made 128. He can't be going too bad," he added.

Kerr also said the injured star is ahead of his recovery schedule, which he attributed to his strong work ethic.

"Any nervous energy he's had around it he tends to channel into enthusiasm. He's working extremely hard. He's a workaholic, an absolute workaholic, and a perfectionist. I think, the way he's going at the moment, he's definitely ahead of schedule," Kerr noted.

Kerr said Clarke performed well in his first outing since surgery after being injured in the first Test against India in December. Clarke scored a half-century for club side Western Suburbs Saturday.

"It all went really well," he said. "Afterwards we did a bit of massage and got into the pool, which was a bit chilly, almost semi like an ice bath. He pulled up really well."